The most common proton conductors are obtained by doping water with an acid such as HCl or H.sub.2 SO.sub.4, or a base such as KOH or NH.sub.3. Thus, aqueous solutions of sulfuric acid have a high proton conductivity greater than 10.sup.-2 S.multidot.cm.sup.-1 and solutions of potassium hydroxide which are also very conducting are widely used as electrolytes in Nickel-Cadmium.
Proton conductors requiring the presence of water in order to function generally have a field of use limited in temperature due to the evaporation of the water and a field of redox stability limited to that of water. The presence of water also usually induces corrosion phenomena within the systems utilizing these electrolytes.
In order to overcome these redhibitory problems with respect to certain applications, a number of works have born on the study of anhydrous proton conductors. From the various classes of materials resulting from these researches, there have been more particularly obtained anhydrous proton conductors by substituting the aqueous solvent with non-hydroxylic solvating polymers such as polyethylene oxide, polyvinylpyrrolidone, polyethyleneimine or polyaminopropylsiloxane.
By doping these polymers with acids or bases, one obtains anhydrous proton conductors. For examples, dissolving orthophosphoric acid H.sub.3 PO.sub.4 in polyethylene oxide (POE) enables one to obtain an acidic proton conductor, and dissolving sulfonamide H.sub.2 NSO.sub.2 NH.sub.2 in the same polymer enables one to obtain a basic proton conductor.
These electrolytes are useful for making electrochemical systems, particularly light-modulating systems, but they still have major drawbacks. Proton conductors obtained by dissolving H.sub.3 PO.sub.4 in POE are corrosive due to the high acidity of the medium (pK.sub.a .apprxeq.0). On the contrary, the high basicity (pK.sub.a .apprxeq.11-12) of proton conductors obtained by dissolving sulfonamides in POE limits their uses. Indeed, in the presence of many electrode materials containing metallic species, there is formed a passivation layer which is a poor conductor of metallic cations complexed with sulfamide. On the other hand, these electrolytes are poor conductors at low temperature.